The universal tempo of animal communication
From insects to great apes, and everything in between, including birds and fishes, animals communicate with a wide variety of sounds. If the pitch of their vocalizations has an importance, rhythm could also have a fundamental role. Scientists from the University of Geneva (UNIGE), the NCCR Evolving Language, the Institut reConnect and the Institut Pasteur analysed more than 2’000 sound recordings emitted by 98 animal species. All vocalize according to a surprisingly similar rate, about two to three vocalizations per second, regardless of their size, environment, species, or social complexity. This constraint could probably be linked to the ability of the brain to process auditory stimuli, of which human language is no exception. These results are published in PLOS Biology.
By the University of Geneva
Almost all species vocalise since hundreds of millions of years according to a common rhythm. © Théophane Piette with AI.
To communicate, many animal species rely on acoustic signals, that vary in frequency and pitch. “But what about rhythm? Is there a common tempo, or does it adapt to the characteristics of each species? It is this temporal dimension that we wanted to investigate,” says Anne-Lise Giraud, a full professor at the Faculty of Medicine at the University of Geneva (UNIGE), director of the reConnect Institute, and researcher at the Pasteur Institute, who led this research.
The scientists analyzed sounds produced by 98 species — mammals, birds, amphibians, insects, reptiles and fishes, at least one per suborder — by developing a method to calculate the rhythm of vocalizations in a standardized way, and then assessing which parameters might influence it. “95% of them are between 0.45 and 4.99 vocalizations per second, with a high concentration around 2,8 Hz, a surprising homogeneity for animals in other ways so different,” underlines Théophane Piette, postdoc researcher at the Department of Fundamental Neurosciences at the Medicine Faculty of the UNIGE and first author of the study.”Neither body weight, the lung capacity, the complexity of social relationships, nor the living environment proved to be determining factors. This suggests that this rhythm is shaped by a common, ancient constraint shared across species, rather than by recent adaptations.”
A neuronal explanation
To analyze a sound, the brain must integrate both its overall structure and its details. Scientists therefore hypothesize that auditory systems have evolved around two complementary temporal scales. Slow oscillations, particularly in the delta band (1 to 4 Hz), are thought to provide a long integration window that allows for tracking acoustic sequences and identifying the general structure of sounds. This rhythm also corresponds to that observed in many animal vocalizations. Conversely, faster processes, likely in the low-gamma bands, would allow for fine temporal discrimination of sounds and the analysis of their detailed acoustic structure. These rapid mechanisms would contribute, in particular, to the identification of speakers or sound sources.
Towards an interspecies communication?
Humans are no exception to this universal rule. Though our speech rhythm is slightly superior to the animal mean — partly due to the structure of language in syllables, words and sentences — we naturally slow down when communicating in challenging situations: when there is background noise, or when speaking with an elderly person or a young child.
This common rhythm could have another consequence: facilitating communication between species. If most of the animals emit and receive on the same base rate, they could decode the signals produced by other species. This is exactly what dogs and humans do: dogs process human speech at the same slow rhythm, and humans tend to reciprocally slow down their flow when they are addressing them. “This common rhythm might not only reflect the way brains process sounds; it could also constitute a sort of universal synchronization that facilitates communication between species,” concludes Théophane Piette.
This study is part of the work carried out by the NCCR Evolving Language, co-led by the Universities of Geneva, Zurich, and Neuchâtel, which aims to understand the biological foundations of language, its evolutionary origins, and the challenges posed by new technologies.
